Method of making artificial fibers or threads from viscose



April 29, 1952 G, A, g JR 2,594,496

METHOD OF MAKING ARTIFICIAL FIBERS OR THREADS FROM VISCOSE Filed April 12, 1949 INVENTOR. GEORGE A. R/CHTERgdr:

Patented Apr. 29, 1952 METHOD OF MAKING ARTIFICIAL FIBERS OR THREADS FROM VISCOSE George A. Richter, Jr-., Springfield, Pa., assignor to American Viscose Corporation, Wilmington, DeL, acorporationoi Delaware,

Application April 12, 1949; .Sfierial No. 87,088

7 Claims.

This. invention relates to a. methodof making artificial fibers-or threads from viscose.

This. application is a continuation-in-part of my. pending application S. N. 28,369, flledM'ay 211, 1948, now abandoned.

A general object of the invention is to produce purev cellulose xanthatefibers capable of: being stretched, and adapted to use in reactions in! volving the xanthate group, for example reactions with various cross-linking and other agents, or for conversion to fibers of regenerated cellulose having the. characteristic properties of cotton fibers, i. e., low extensibility, especially in the wet state, combined with from good to superior tenacity.

In accordance with the invention, viscose is spun into an essentially aqueous coagulating medium which is not a cellulose regenerating medium and which contains both acetic acid and either sodium sulfate, sodium acetate, or a mixture of sodium sulfate and sodium acetate,. and the continuous filaments of cellulose xanthate thus obtained are withdrawn fromv the coagulating bath and given the maximum stretch which" the filaments will accept without rupture, usually 50 to 200% The viscose. by-products are broken downin the bath containing acetic. acid and thefilaments or threads withdrawn from the bath comprise substantially pure cellulose xanthate.

Generally, the bath contains from 1 to -20%.ofv

diumsulfate and/or sodium acetate content of the bath may vary within the range stated, but since-acetic acid, sodium sulfate, and sodium acetate all exert a dehydrating action on the viscose, the total concentration of these components, or of the two components, when the bath contains only the acetic acid and sodium sulfate or sodium acetate must be at, least 15%. The bath must contain both the acetic acid and the sodium sulfate and/or sodium acetate. The filaments obtained by the process of this invention cannot be obtainedby extruding the viscose into a coagulating bath containing either the acetic acid orany other organic acid alone, or the sodium sulfate and/or sodium acetate alone.

The salt point (sodiumchloride) of the viscose may-be from 3' to 12, and is preferably from 4 to about 6, which is the sodium chloride salt point at which viscose is usually spun.-

Regardless of the concentration of acetic acid in the bath, at the start of operations, it decreases as spinning proceeds. In order to maintain the acetic acidat the selected concentration, the requiredamou-nts of acetic acid as such may be'added'to the bath or sulfuric acid may be added in calculated amounts to displace acetic acid iromthe sodium acetate formed as byproduct, andproduce sodium sulfate.

The cellulose xanthate fibers produced by the present'method yield, after stretching and treatment with a'cellulose regenerating medium, regenerated cellulose filaments or yarns which are characterized by low extensibility, especially low extensibility in the wet state, and from good to superior tenacity. The wet and dry extensibilities are from 4 to 8%. These, extensibilities distinguish-the present fibers or'yarns from fibers or yarns of regenerated cellulose produced from viscose by the conventional single bath processes, which have a wet extensibility of from 16 to 35%, and. dry extensibility of 15 to 25%. The tensile strengthsof the fibers or yarns of the invention .are from 3 to as high as 4.5 gms./denier dry; from 2 to 3.5 .gms/denier wet. In general, the tenaci ties increase as the cellulose-to-sodium hydroxide ratio is increased, the acetic acid content of the bath being. simultaneously decreased. The maximum cellulose-to-sodium hydroxide ratio which can be used is dependent on the maximum viscosity of the viscose which it ispractical to use with available equipment. Consequently, it is usually impractical to exceed a cellulose-to-sodium hydroxide ratio of 2:1.

The regenerated cellulose fibers obtained by the present method are ovoid in cross-section and contain numerous small voids which occur throughout all portions of the cross-section. Microscopic examination of the cross-section does not reveal a skin on the fibers such as present on' normal regenerated cellulose fibers. The fibers do not shrink or contract when they are immersedin water, and have been. found to 'elon-' gate only 1.5 to 5% at the loads of 1 gm./denier.

The invention is illustrated in the accompanying drawing in whichv Figure 1 is. a diagrammatic showing of one specific embodiment, and.

Figure 2 is a diagrammatic showing of another specific embodiment.

As shown in 'Fig. 1, viscose is extruded through a spinneret 2 into a vessel 3 containing an aqueous bath which is a coagulating bath for cellulose xanthate and which does not regenerate cellulose, the bath comprising from 1 to 20% by Weight of acetic acid and from to 30% by weight of sodium sulfate, sodium acetate, or a mixture of sodium sulfate and sodium acetate. After the normal immersion in the bath, the continuous filaments are withdrawn and passed under the guide 4 to the godets 5 and 6. The filaments are wrapped one or more times around the godets, thread displacing guides 1 being provided adjacent godets 5 and 6 for that purpose. The filaments are given a stretch of from 50 to 200% between the godets, and in order to accomplish this, godet 6 may be rotated at a peripheral speed higher than the peripheral speed of godet 5, or the godets may be of different sizes. From godet 6, the filaments are passed through vessel 8 containing a cellulose regenerating bath which may be, for example, an aqueous bath containing sulfuric acid and sodium sulfate, and which may also contain other constituents commonly present in regenerating baths such as zinc sulfate or the like. After withdrawal from the regenerating bath, the filaments may be treated with the usual after-treating liquids and collected for use as such or they may be sent to a cutting mechanism for cutting into discontinuous fibers. Alternatively, the filaments leaving the regenerating bath may be sent directly to the cutting mechanism, in which case they are treated with the usual after-treating liquids after the cutting operation. In the embodiment shown in Fig. 2, the filaments are withdrawn from the bath, passed under the guide 4 to godet 9 and then over the godet I0, thread displacing guides l2 being provided adjacent godets 9 and ID. The filaments passing between the godets are given a stretch of from 50 to 200%. A vessel H containing the cellulose regenerating bath is supported in the path of travel of the filaments between the godets. The regenerated cellulose filaments leaving godet 10 are subjected to the after-treating liquids or are sent directly to a cutting mechanism and then subjected to the after-treating liquids, i. e., desulfurizing, bleaching, washing liquids. Alternatively, the cellulose xanthate filaments leaving the coagulating bath may be advanced over a thread handling, thread storage device on which they are given the required stretch and subjected to the after-treating liquids.

The regenerated cellulose fibers produced by the method of this invention are comparable to cotton fibers and can be used for purposes for which regenerated cellulose fibers have not heretofore been adapted. Fabrics made from yarns spun from the fibers compare most favorably with cotton fabrics. The outstanding advantage of cotton fabrics over the rayon fabrics constructed from yarns of normal regenerated cellulose fibers is the resistance to deformation on stretching which is characteristic of cotton fabrics. The fabrics formed from yarns spun from the regenerated cellulose fibers produced in accordance with this invention exhibit the resistance to deformation on stretching and resistance to loss of shape which is possessed by cotton fabrics. Yarns of these regenerated cellulose fibers may be woven into fabrics which are useful as shirting fabric, and the shirts made from the fabrics do not lose their shape during laundering. The regenerated cellulose fabrics are also useful as fillers for laminated 4. resin articles or for any other purpose for which high strength and. resistance to dimensional change are primary requisites.

Example I A viscose normal viscosity and having a. cellulose-to-sodium hydroxide ratio of 1.05:1 and a salt point (sodium chloride) of 4.4 was spun into an aqueous coagulating bath containing 10% by weight acetic acid and 10% by weight sodium sulfate, at 50 C., using a spinneret having 200 holes, each hole having a diameter of 0.0025. The filaments were given an immersion of 5" in the coagulating bath. The cellulose xanthate threads were withdrawn from the bath and given the maximum stretch which they would accept short of rupture after which they were passed through a cellulose regenerating bath comprising an aqueous solution of 20% by weight sulfuric acid and 10% by weight sodium sulfate, the bath having a temperature of about 40 C. The 150 denier yarn was collected at 60 meters per minute in a spinning box revolving at 7,000 R. P. M., whereby the yarn was given a twist of about 3 turns per inch. The yarn was then washed, desulfided, bleached and finished in the usual manner. The finished yarn had the following properties:

. Elongation Tensile at Break Cross- Strength Percent lgltoggafon liltoiiggalton g l l W0 111?, D r y Wet Percent Dry Wet Dry Wet Example II A viscose of normal viscosity and having a cellulose-to-sodium hydroxide ratio of 1.05:1 and a salt point (sodium chloride) of 4.0 was spun into an aqueous coagulating bath containing 13% by weight acetic acid and 13% by weight sodium 0 sulfate at C. using a spinneret containing 120 holes, each hole having a diameter of 0.0025". The filaments were given an immersion of 5" in the co'agulating bath, and the cellulose xanthate filaments were then withdrawn from the bath and given the maximum stretch short of rupture (about 200%). Regeneration of the cellulose was effected while the filaments were being passed between the stretching godets, the regenerating medium comprising an aqueous solution containing 10% by weight sulfuric acid and 10% by weight sodium sulfate at about 40 C. The 150 denier yarn was collected and treated as in Example I. The properties of the resulting yarn were as follows:

- Elongation Tensile Strength 2 Elongation Elongation 3 23a at 2 g./d., at 1 g./d., Swelling Dry Percent Dry Wet Dry Wet This yarn was woven into a taffeta fabric which was found to have much greater dimensional stability than a comparable normal rayon fabric.

Example III A viscose of normal viscosity and having a cellulose-to-sodium hydroxide ratio of 1.05:1and

a salt point (sodium chloride) of 6.9 was spun into an aqueous coagulating bath containing 15% byweight acetic acid and 20% by weight sodium sulfate, at 50 C., using a spinneret having 150 holes, each hole having a diameter of 0.0025". The filaments were given an immersion of 10" in the coagulating bath, The cellulose xanthate threads were withdrawn from the bath and given the maximum stretch, after which they were passed through a cellulose regenerating bath comprising an aqueous solution of 20% by weight sulfuric acid and 10% by Weight sodium sulfate, and the bath having a temperature of about 50 C. The 150 denier yarn was collected at 60 meters per minute in a spinning box revolving at 7000 R. P. M., whereby the yarn was given a twist of about 3 turns per inch. The yarn was then washed, desulfided,- bleached and finished'in the usual manner. The finished yarn had the follow- A viscose of normal viscosity and having a cellulose-to-sodium hydroxide ratio of 1.05:1 and a salt point (sodium chloride) of about 4.0 was spun into an aqueous coagulating bath containing 13% by weight acetic acid, 8% by weight sodium sulfate and 5% by weight sodium acetate, at 50 C., using a spinneret having 120 holes, each hole having a diameter of 0.0025. The filaments were given an'immersion of 3" in the coagulating bath. The cellulose Xanthate threads were withdrawn from the bath and given maximum stretch, during which they were passed through a cellulose regenerating bath comprising an aqueous solution of 10% by weight sulfuric acid and 10% by weight sodium sulfate, the bath having a temperature of about 15 C. The 150 denier yarn was collected and processed as in the above ex- Same as Example IV except that the coagulating bath contained 13 by weight acetic acid, 5 by weight sodium sulfate and 3% by weight sodium acetate. The finished yarn had the following properties:

- Elon ation Tensile Strength 3553? Elongation Elongation 551 535 7 at 2 g./d., at l g./d., Swelling Dry et Percent Dry Wet Dry Wet Example VI Same as Example IV except that the coagulating bath contained 13 by weight acetic acid and 13% by weight sodium acetate. The finished yarn had the following properties:

- Elongation I Tensil at Break 11 Cross 5 Strength Percent g g yg E Pf Sectional i E- g Swelling, 1

Percent Dry Wet Dry Wet Example VII A viscose of normal viscosity and composition (cellulose-to-sodium hydroxide ratio less than 1:1), and having a salt point (sodium chloride) of about 4.0 was spun into an aqueous coagulating bath containing 13% by weight acetic acid and 13% by weight sodium sulfate at 50C., using a spinneret having 980 holes, each hole having a diameter of 0.0025". The filaments were given an immersion of in the coagulating bath. The cellulose xanthate threads were withdrawn from the bath and given maximum stretch during which they were passed through a cellulose regenerating bath comprising an aqueous solution of by weight sulfuric acid and 10% by weight sodium sulfate, the bath having a temperature of about 45 C. The 500 denier yarn was collected and processed as in the Example III. The ffin ished yarn had the followingproperties:

1 Calculated from actual filament count.

Example VI II A viscose of normal viscosity and composition (cellulose-to-sodium hydroxide ratio less than 1:1), and having a salt point (sodium chloride) 3 of 10.0 was spun into an aqueous coagulating bath containing by weight acetic acid and 10% by weight sodium sulfate, at C., using a spinneret having 120 holes, each hole having a diameter of 0.0025". The filaments were given 59 an immersion of '7" in the coagulating bath. The

cellulose xanthate threads were withdrawn from the bath and given the maximum stretch they would accept short of rupture after which they were passed through a cellulose regenerating bath comprising an aqueous solution of 15% sulfuric acid and 10% sodium sulfate at 50 C. The

150 denier yarn wa collected at 70 meters per minute in a spinning box revolving at 7000' R. P. M., whereby the yarn was given a twist of 60 about 3 turns per inch. The yarn was then washed, desulfided, bleached and finished in the usual manner. The finished yarn had the following properties:

Tensile Elongation Strength Percent Elongation at Elongation at 2 g./d., l

Dry

Dry Wet Dry Wot Example IX Same as Example VIII except that the viscose used was prepared from unmercerized soda cellulose. This viscose had a ball fall of about 230 seconds as compared to about 60 seconds for normal viscose. The finished yarn had the follow ing properties:

A viscose containing about 8% and about 6.5% sodium hydroxide, and having a salt point (sodium chloride) of 4.3 was spun into an aqueous coagulating bath containing 5% by weight acetic acid and 20% by weight sodium sulfate, at 40 C., using a spinneret having 120 holes, each hole having a diameter of 0.0025". The filaments were given an immersion of 5" in the coagulating bath. The cellulose xanthate threads were withdrawn from the bath and given the maximum stretch they would accept without rupture after which they were passed through a cellulose regenerating bath comprising 15% by weight sulfuric acid and 15% by weight sodium sulfate, the

bath having a temperature of about 40 C. The 280 denier yarn was collected at 60 meters per minute in a spinning box revolving at 7000 R. P. M., whereby the yarn was given a twist of about 3 turns per inch. The yarn was then washed, desulfided, bleached, and finished in the usual manner. The finished yarn had the following properties:

Example X was repeated, except the viscose had a salt point (sodium chloride) of 5.7. The yarn had the following properties:

Tensile Strength, g./d. Elongation, Percent Dry Wet Dry Wet Example XII A viscose containing about 8% cellulose and about 6.5% sodium hydroxide, and having a salt point (sodium chloride) of 4.3 was spun into an aqueous coagulating bath containing by weight acetic acid, 15% by weight sodium sulfate and 10% by weight sodium acetate, at 50 C., using a spinneret having 120 holes, each hole having a diameter of 0.0025. The filaments were given an immersion of 12" in the coagulating bath. The cellulose xanthate threads were withdrawn from the bath and given the maximum godet stretch they would accept without rupture after which they were passed through a cellulose regenerating bath comprising 15% by weight sulfuric acid and 15% by weight sodium sulfate, the bath having a temperature of about 40 C. The 280 denier yarn was collected at meters per minute in a spinning box revolving at 7000 R. P. M., whereby the yarn was given a twist of about 3 turns per inch. The yarn was then washed, desulfided, bleached and finished in the usual manner. The finished yarn had the following properties:

Tensile Strength, gI/d. Elongation, Percent Dry 'Wet Dry V81 As will be noted from Example VII, it is possible, by the present method using a coagulating bath consisting of an aqueous solution of acetic acid and sodium sulfate, sodium acetate, or mixed sodium sulfate and sodium acetate, to spin filaments of very low denier per filament. Filaments of less than denier/filament have been spun by the present method over along period of time, without difliculty. As is Well known, it is difllcult to spin filaments of less than 1 denier/filament, by conventional spinning processes. This possibility of spinning filaments of extremely low denier per filament without diflilculty is an additional advantage of the present invention, as compared to the conventional methods.

Variations and modifications may be made in carrying out the invention Without departing from the spirit and scope thereof, and the invention is not to be limited, therefore, except as defined by the appended claims.

I claim:

1. In the manufacture of artificial fibers from viscose, the steps which comprise extruding the viscose into an essentially aqueous coagulating medium which is not a cellulose regenerating medium and which contains from 1 to 20% by weight of acetic acid and from 5 to 30% by weight of salt selected from the group consisting of sodium sulfate, sodium acetate and mixtures of sodium sulfate and sodium acetate, the total concentration of salt and acetic acid being at least 15% by weight, withdrawing the continuous filaments of cellulose xanthate thus obtained from the bath, and stretching the filaments.

2. A method of making artificial fibers or yarns from viscose comprising extruding the viscose into an essentially aqueous coagulating medium which is not a cellulose regenerating medium and which contains from 1 to 20% by weight of acetic acid and from 5 to 30% by weight of salt selected from the group consisting of sodium sulfate, sodium acetate, and mixtures of sodium sulfate and sodium acetate, the total concentration of salt and acetic acid being at least 15% by weight, withdrawing the continuous filaments of cellulose xanthate thus obtained from the bath, stretching the filaments, and treating the filaments with a cellulose-regenerating medium to obtain regenerated cellulose filaments.

3. A method as in claim 2, wherein the cellulose-to-sodium hydroxide ratio of the viscose is about 1:1.

4. A method as in claim 2, wherein the viscose has a sodium chloride salt point of from 3 to 12.

5. A method as in claim 2, wherein the viscose has a sodium chloride salt point of 4 to 6.

6. A method as in claim 2, wherein the viscose has a cellulose-to-sodium hydroxide ratio of less than 1:1, a sodium chloride salt point of about 4.3, and is extruded into a coagulating medium REFERENCES CITED cntaining.5% acetic acid and 20% Sodium $111 The following references are of record in the fate'by Welghtfile of this patent:

'7. A method as in c1a1m 2, wherein the viscose has a cellulose-to-sodium hydroxide ratio of 1.05 5 UNITED STATES PATENTS to 1, a sodium chloride salt point of about 4.3, Number Name Date and is extruded into an aqueous coagulating me- 792,888 Ernst June 20, 1905 dium containing 5% acetic acid, 15% sodium sul- 2,328,307 Thurmond et a1. Aug. 31, 1943 fate, and 10% sodium acetate, by weight.

GEORGE A. RICHTER, JR. 10 

1. IN THE MANUFACTURE OF ARTIFICAL FIBERS FROM VISCOSE, THE STEPS WHICH COMPRISE EXTRUDING THE VISCOSE INTO AN ESSENTIALLY AQUEOUS COAGULATING MEDIUM WHICH IS NOT A CELLULOSE REGENERATING MEDIUM AND WHICH CONTAINS FROM 1 TO 20% BY WEIGHT OF ACETIC ACID AND FROM 5 TO 30% BY WEIGHT OF SALT SELECTED FROM THE GROUP CONSISTING OF SODIUM SULFATE, SODIUM ACETATE AND MIXTURES OF SODIUM SULFATE AND SODIUM ACETATE, THE TOTAL CONCENTRATION OF SALT AND ACETIC ACID BEING AT LEAST 15% WEIGHT, WITHDRAWING THE CONTINUOUS FILAMENTS OF CELLULOSE XANTHATE THUS OBTAINED FROM THE BATH, AND STRETCHING THE FILAMENTS. 